1. Field
The present disclosure relates to zoom lens systems, interchangeable lens apparatuses, and camera systems.
2. Description of the Related Art
In recent years, interchangeable-lens type digital camera systems (also referred to simply as “camera systems”, hereinafter) have been spreading rapidly. Such interchangeable-lens type digital camera systems realize: taking of high-sensitive and high-quality images; high-speed focusing and high-speed image processing after image taking; and easy replacement of an interchangeable lens apparatus in accordance with a desired scene. Meanwhile, an interchangeable lens apparatus having a zoom lens system that forms an optical image with variable magnification is popular because it allows free change of focal length without the necessity of lens replacement.
Zoom lens systems having excellent optical performance from a wide-angle limit to a telephoto limit have been desired as zoom lens systems to be used in interchangeable lens apparatuses. For example, various kinds of zoom lens systems, having a multiple-unit configuration in which a negative lens unit is located closest to an object side, have been proposed.
Japanese Laid-Open Patent Publications Nos. 2012-027262, 2011-170371, and 2010-054722 each discloses a lens system having a four-unit configuration of negative, positive, negative, and positive, in which the first to third lens units move along the optical axis in zooming, and focusing is performed by the third lens unit or the fourth lens unit.
Japanese Laid-Open Patent Publication No. 2008-233611 discloses a lens system having a four-unit configuration of negative, positive, negative, and positive, in which at least the second lens unit and the third lens unit move along the optical axis in zooming, and focusing is performed by the third lens unit.
Japanese Laid-Open Patent Publication No. 2001-343584 discloses a lens system having a four-unit configuration of negative, positive, negative, and positive, in which the first lens unit and the second lens unit move along the optical axis in zooming, and focusing is performed by the third lens unit.